Propellant compositions



United States Patent 3,352,727 PROPELLANT COMPOSITKONS Robert A. Cooley, Rosewood Heights, 111., assignor to Chromalloy Corporation, St. Louis, Mo., a corporation of New York No Drawing. Filed Mar. 16, 1962, Ser. No. 180,329 7 Claims. (Cl. 149-49) This invention relates generally to propellant compositions and particularly to solid propellant compositions useable in the aircraft and missile fields.

Solid propellant compositions are providing important new innovations as energy sources for auxiliary power units in the aircraft and guided missile fields. Their high energy content per unit of weight, and the relative simplicity of the solid propellant gas generators combine to give low airborne weight, high reliability and freedom from major maintenance problems. One of the most important advance that can be made in a gas generator type solid propellant is the reduction of its temperature coelficient. In present day designs of gas generators, various kinds of mechanical equipment, such as various controls, are necessary due to the high temperature coefficient that these propellants show. Much of this mechanical equipment can be obviated, and possible wider application of the solid propellants can be made by providing a solid propellant composition with a low temperature coefi'icient.

It is therefore an object of the present invention to provide a solid propellant composition which is highly reliable, possesses a superior temperature coeflicient, a suitable burning rate and excellent physical properties for use in solid propellant gas generators.

Another object is to provide a solid propellant composition which possesses a low temperature coefficient.

Other objects will appear obvious to those skilled in the art from the following detailed description, which is in such full, clear and exact terms that any person can make and use the same.

Most solid propellant compositions fall into two general types, one being the double base type which uses nitroglycerine and nitrocellulose, and the other being the composite type which uses a crystalline oxidizer and various binders and modifier components. The solid propellant compositions of the present invention are of the composite type using ammonium nitrate as the oxidizer.

The ammonium nitrate is present within the composition in an amount between about 65 and about 8 0% by weight and is bound together by the use of a polymeric material such as butadiene acrylic acid (Hycar 1000X103) in an amount between about 10 to about 18% by weight. Other additives such as ballistic modifiers and plasticizers are normally added to the propellant composition, such additives as have been used by those skilled in the art are guanidine nitrate, ammonium oxalate, sodium barbiturate and carbon black, among others. These additional additives, combined, represent from about 10 to of the total composition, by weight.

Solid propellant compositions containing the above named ingredients, frequently have a temperature coefiicient in the order of .23%/ F. One of the important aspects of the present invention is that by the addition of a small amount of a burning rate temperature coeflicient 3,352,727 Patented Nov. 14, 1967 "ice reduction agent to the other ingredients, heretofore mentioned, that a solid propellant composition possessing a far superior temperature coefficient (about 50% lower) is obtained.

The burning rate temperature coefficient reduction agents, within the purview of the present invention are selected from the group consisting of triethylene glycol dinitrate (TEGDN) and di-n-octyl decyl adipate (DNODA). The quantity of these ingredients can vary from about 1 to about 5%, by weight of the total propellant composition and may be present either alone or in combination with one another.

The solid propellant compositions Within the purview of the present invention have a density of about .05 lb./in. They have a burning rate which varies from about .040 in. per second up to about .108 in. per second, depending upon the combustion pressure, the particular temperature and the mixture of the composition. The average temperature coefficient is about .171 taken over a temperature span of about 200 degrees Fahrenheit.

The flame temperature of these propellants is about 2000 F., and the exhaust gas has very little smoke associated with it. The physical properties of these solid propellants makes them extremely desirable for gas generator type propellants.

The following examples are presented for the purpose of exemplifying some of the solid propellant compositions which are within the purview of the present invention, but the invention is deemed not to be limited thereby.

Example I A solid propellant composition containing, indicated as percent by weight:

Percent Ammonium nitrate 72 Butadiene acrylic acid 14 Guanidine nitrate 4 Ammzonium oxalate 44- Sodium barbiturate 2 Carbon black 2 Di-n-octyl decyl adipate 2 was prepared according to the following method.

14 pounds of butadiene acrylic acid (Hycar IOOOXIOB) is cut into .5 cubes and mixed with 24.5 pounds Skelly solve B solvent (hexane) in a closed sigma blade mixer for 15 minutes in order to soften and swell the rubber.

All remaining ingredients after being ground through a .020" herring bone screen are added to the rubber in the mixer and with the lid on, mixed for two hours at about F.

Solvent is then removed by continuing the mixing at atmospheric pressure for 30 minutes and raising the mix to 180 F. A vacuum is applied to the mixer and the solvent is completely removed by 30 minutes mixing under vacuum.

The crumbs of composition at 180 F. are then compacted into grains under a pressure of 600 p.s.i. for 10 rriinutes. This composition has a temperature coefiicient o .144.

Other specific embodiments of the present invention are set forth in the following table. These compositions were made in the same general manner as set forth in Example I.

TABLE I r Example Ingredients Many different binding materials have been employed by those skilled in the art to bind the various ingredients together. Modified synthetic rubbers as well as certain monomeric materials such as acrylates have been successfully used. These binding materials also serve as a fuel for the propellant. The preferred binding material as set forth in the examples is butadiene acrylic acid (Hycar 1000X103).

The temperature coefiicient, as used in the above-description and appended claims, is calculated at a given pressure and over a temperature range of about 200 degrees, by subtracting the slowest burning rate from the fastest burning rate, dividing the result by the base burning rate (slowest burning rate), dividing by the number of degrees in the temperature range and multiplying the resulting quotient by 100 to obtain the percent increase per degree. As a specific example of this, the composition of Example I, at a combustion pressure of 1000 p.s.i., had a burning rate of .065 in./sec. at -40 F. and a burning rate of .084 in./sec. at 160 F., thus Many modifications of and changes in the composition of the present invention may be made without departing from the spirit of the invention or sacrificing any of its advantages.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. A solid propellant composition consisting essentially of ammonium nitrate, butadiene acrylic acid, guanidine nitrate, ammonium oxalate, sodium barbiturate, carbon black and a burning rate temperature coefiicient reduction agent selected from the group consisting of triethylcne glycol dinitrate and di-n-octyl decyl adipate.

2. The solid propellant composition of claim 1 wherein the essential ingredients are present within the composition in the amount of, by weight, ammonium nitrate about 65 to 80%, butadiene acrylic acid about 10 to 18%, burning rate temperature coefficient reduction agent about 1 to 5%, others combined about to 3. A solid propellant composition consisting of, percent by weight,

Percent Ammonium nitrate 72 Butadiene acrylic acid 14 Guam-dine nitrate 4 Ammonium oxalate 4 Sodium barbiturate 2 Carbon black 2 Di-n-octyl decyl adipate 2 4. A solid propellant composition consisting of, percent by weight,

5. A solid propellant composition consisting of, percent by weight,

Percent Ammonium nitrate 72 Butadiene acrylic acid l4 Guanidine nitrate 4 Ammonium oxalate 4 Sodium barbiturate 2 Carbon black 1 Triethylene glycol dinitrate 3 6. A solid propellant composition consisting of, percent by weight,

Percent Ammonium nitrate 72 Butadiene acrylic acid 14 Guanidine nitrate 4 Ammonium oxalate 4 Sodium barbiturate 2 Carbon black 1 Di-n-octyl decyl adipate 3 7. The solid propellant composition of claim 1 wherein the burning rate temperature coefiicient reduction agent consists essentially of both triethylene glycol dinitrate and di-n-octyl decyl adipate.

References Cited UNITED STATES PATENTS 2,988,435 6/1961 Stanley et al. 149-19 2,997,375 8/1962 Rumbel et a1. 149-19 2,966,403 12/1960 Weil 149-19 2.995,430 8/1961 Scharf 149-19 2,938,780 5/1960 Proell et al. 149-19 BENJAMIN R. PADGETT, Primary Examiner.

OSCAR R. VERTIZ, CARL D. QUARFORTH,

Examiners. 

1. A SOLID PROPELLANT COMPOSITION CONSISTING ESSENTIALLY OF AMMONIUM NITRATE, BUTADIENE ACRYLIC ACID, GUANIDINE NITRATE, AMMONIUM OXALATE, SODIUM BARBITURATE, CARBON BLACK AND A BURNING RATE TEMPERATURE COEFFICIENT REDUCTION AGENT SELECTED FROM THE GROUP CONSISTING OF TRIETHYLENE GLYCO DINITRATE AND DI-N-OCTYL DECYL ADIPATE. 